|
The same ocean currents existed in 1912 as they do today. But ocean currents are not stationary. They shift over time, usually taking several days to make a small enough changes to be noticeable. Thanks to modern day satellite radar imaging, these shifts can be seen and tracked over time. For example, the animation below shows how the Gulf Stream changed in 7 day increments over a period of 26 weeks from 24 June 2011 to 16 December 2011. The colors show the speed of the current (not the water temperature) at any given point, and the little arrow vectors show the direction of the current at that point. The speed scale is in meters per second (m/s), and the conversion to knots is 1.94 knots per m/s. (The date of each frame is shown in the upper left side in the format yymmdd; thus, 110624 is the situation for 24 June 2011.) |
|
|
Pilot charts for an area of ocean give long term averages of the current in that area for a given month. The arrows on the pilot charts indicate the prevailing direction, and the numerals show the mean current speed in knots. They can be used to show what might be expected along a certain route of travel. For example, at local apparent noon (LAN) for 14 April 1912, Titanic was approximately at 43° 02’ N, 44° 31’ W at 14:58 GMT, or about 126 nautical miles before the corner point at 42° N, 47° W. Her course to the corner would be about 241° true. Over the previous 24h 45m, from LAN 13 April to LAN 14 April, Titanic ran 546 nautical miles averaging 22.06 knots. However, we are told that Capt. Smith set the time to alter Titanic’s course upon reaching the corner at 5:50pm Apparent Time Ship (ATS), or 5h 50m past LAN. If we divide the distance to the corner by that time interval we get a speed of 21.6 knots, or ½ knot less than what the ship averaged the day before despite carrying the same number of revolutions per minute on her engines. Pilot charts for April show current vectors pointing about ENE true at 0.5 knot for Titanic’s position at LAN that day. It seems that Capt, Smith had allowed for a ½ knot head current in setting the time to alter the ship’s course at the corner.
But did Titanic actually encounter a ½ knot current in her run from LAN to the corner that day? If we add the distance from LAN to the corner to the distance from the corner to a collision point taken just north of the wreck site at 41° 46’N, 49° 56’W [see Collision Point], we find a total distance made good of about 258 nautical miles, a distance consistent with a taffrail log reading that showed that the ship traveled 260 miles through the water over that path. To cover 258 miles in 11h 40m from LAN to the time of collision, the ship would have averaged 22.11 knots, about the same as she was doing since noon on Saturday, 13 April. So it seems that Titanic had not been slowed down by the expected Gulf Stream current in that area after all. But if not, why not?
The answer lies in the fact that the Gulf Stream is far from being a stationary current. Looking at satellite radar imaging taken over a period of nine years for the 14th of April, we see a great amount a variability in the Gulf Stream and other currents in the area. This data is shown in the following sequence of images for 14 April from 2003 through 2011. Superimposed on these radar images is the route that Titanic was following on 14 April 1912, including her LAN position for 14 Apr 1912, the alter course point at the corner (42°N, 47°W), the wreck site location, and the intended arrival points at the Nantucket Shoals and Ambrose Channel light vessels near the North American coast. |
|
|
Of particular interest, notice the area of the corner for 14 April 2005 which is expanded in the image to the right. Notice that from the location of Titanic’s 1912 LAN position to the corner, the track would pass through an area where the current was running north-northwest, part of a clockwise eddy flow in that particular region. This component, running perpendicular to the track line, would not have slowed a ship’s forward progress toward the corner. It would, however, set a vessel traveling at 22 knots perhaps a mile to the NNW of the track line based on the strength of current shown and the width of the area that a ship would be passing through. Beyond the corner to the wreck site location, a current on 14 April 2005 was almost non-existent.
What the situation was on 14 April 1912 we of course cannot say for certain. But what we can see from these modern day satellite radar images is that currents in this part of the Atlantic are anything but predictable. And even less predictable is when you find two strong currents converging like that shown in the second image to the right where a we see a strong Labrador current converging with a strong Gulf Stream flow in the vicinity of the corner. Given the measured southerly drift of wreckage seen on the morning of 15 April 1912, as well as temperature data taking by the SS Californian showing a sudden 20°F drop in water temperatures to freezing levels west of longitude 48° 30’W, it is clear that the Labrador was dominant in the region which caused all that ice to drift far to the south, reaching as far south as 41° 16’N as documented by Carpathia. It is also probable that the general current flow coming down from the Labrador would have looped around counter clockwise into a northeasterly flow similar to that shown in the upper part of the image on the right. |
|
